What's the main difference between "sales" and "revenue?"

Native speaker’s answer
Rebecca
Revenue is all the income a company generates before any expenses are subtracted. Sales is the amount a company generates from selling goods or services to its customers. Sales is a part of revenue, but not necessarily the only source of revenue. So you can think of sales as being operating revenue, whereas revenue is the total revenue. Ex: Sales make up 90% of our total revenue. Ex: Sales have been down this month, so it's going to affect our revenue.